Table 1:

Description of SIBS sample

Sample	Number of individuals	M age at intake (SD)	M age at follow-up 3 (SD)
Parents
Mothers	419	46.6 (4.2)	63.9 (4.8)
Fathers	201	48.2 (4.4)	65.4 (4.7)
Adopted offspring
Female	235	15.2 (2.2)	32.5 (2.8)
Male	127	14.8 (1.8)	31.6 (2.5)
Biological offspring
Female	186	14.9 (1.9)	31.5 (2.5)
Male	120	14.8 (1.8)	31.1 (2.6)

Note: Number of individuals listed represents those with valid scores for either Vocabulary or the ICAR-16 at follow-up 3. Valid N for each intake measure are shown in SI Table S2.